IEC 61558-2-4:20 21作为IEC 61558-2-4:20 21 RLV提供，其中包含国际标准及其红线版本，显示了与上一版本相比技术内容的所有变化。IEC 61558-2-4:20 21涉及一般应用隔离变压器和包含一般应用隔离变压器的电源单元的安全性。包含电子电路的变压器也包括在本文件中。这第三版取消并取代了2009年出版的第二版。本版构成技术修订版。与上一版相比，此版本包括以下重大技术变更: -根据IEC 61558-1:20 17调整结构和参考文献； -移至IEC 61558的结构描述-1:2017; -输出电压线性调节的电源单元的新符号。 根据IEC指南104，它具有团体安全出版物的地位。 本国际标准将与IEC 61558-1:20 17结合使用。

IEC 61558-2-4:2021 is available as IEC 61558-2-4:2021 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.

IEC 61558-2-4:2021 deals with the safety of isolating transformers for general applications and power supply units incorporating isolating transformers for general applications. Transformers incorporating electronic circuits are also covered by this document. This third edition cancels and replaces the second edition published in 2009. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
- adjustment of structure and references in accordance with IEC 61558-1:2017;
- description of constructions moved to IEC 61558-1:2017;
- a new symbol for power supply unit with linearly regulated output voltage.
It has the status of a group safety publication in accordance with IEC Guide 104.
This International Standard is to be used in conjunction with IEC 61558-1:2017.